I've seen some people using web2.0 properties as tier 1, and PBN sites linking to those as tier 2. I'm just wondering why this would be better than using PBN sites as tier 1 going directly to money site? I'm thinking that since the web2.0s are more frequently used for spam, wouldn't it be better to just use PBN sites as tier 1? Or is it because of the high DA of web2.0, and getting a PA boost to that page would provide more link juice and value than a PBN site in itself? My question in short: Why would you use PBN sites as tier 2 instead of tier 1?